Machine for coating and drying tape



April 10, 1956 w. c. SPEED Erm.

MACHINE FOR COMING AND DRL/ING TAPE 4 Sheets-Sheet l Original Filed Dec. 2l, 1950 www. 3J mi on.: wm

ON NE (GLM lNvNTo ATTORNEYS w INN! v 5 MT Er Nm @E Nm- April 10, 1956 w. c. SPEED ETAL 2,741,217

MACHINE FOR COATING AND DRYING TAPE Original Filed Dec. 2l, 1950 4 Shees-SheelI 2 ATTORNEYS' April 1o, 1956 W. C. SPEED ETAL MACHINE FOR COATING AND DRYING TAPE Original Filed Dec. 2l. 1950 4 Sheets-Sheet 3 April 10, 1956 w. c. SPEED Erm.

MACHINE Foa COMING AND DRYING TAPE 4 Sheets-Sheet 4 Original Filed Dec NKNN w Ng WEL@ il f United States sa .i

MACHINE FOR COATNG AND DRYING TAPE William C. Speed, Riverside, and Eames l. Dwyer, Stamford, Conn., assignors to Audio Devices, Inc., New York, N. Y., a corporation of New Yer-k Original application December 21, 1958, Serial No. 201,980, now Patent No. 2,762,251, dated February 15, 1955. Divided and this application December 29, 1951, Serial No. 259,371

9 Claims. (Cl. 118-51) This-invention relates to the production of magnetic recording tape and has for its object improvements in the method of and apparatus for drying tape base freshly coated with magnetic material.

'I'his application is a division of copending application Serial No. 201,980 filed December 21, 1950, now Patent No. 2,702,251, dated February l5, 1955, for Production of Magnetic Sound Tape. As therein disclosed, the tape base is passed successively through a series of zones, such as charging or feeding, adhesive pre-coating, precoat drying, magnetic coating, magnetic coat drying, etc. The present application is primarily concerned with the method of and apparatus for drying the magnetic coating.

in the production of magnetic sound recording and reproducing tape it is Vcustomary to pass a relatively long and narrow tape base band successively through one or more coating and drying zones, one side of the tape base being coated with alayer of free-owing magnetic material while moving through the coating zone and the layer being dried While moving through the drying zone. Various tape base materials are used, such as paper, plastics, etc., the most common being paper and cellulose acetate. Various magnetic materials may be used for the coating, the one most commonly used at the present time being very iinely divided magnetic oxide of iron; not the natural magnetic oxide of iron, but one that is produced artificially because its quality can be better controlled. A dispersion of the magnetic material in a suitable vehicle or carrier is prepared, the vehicle usually containing a solvent, such as toluol, isopropyl acetate, etc. The dispersion, while free-iiowing, has a viscosity conducive to the laying down of a coating of given thickness on the tape base which remains substantially intact during the drying operation. The solvent is volatilized during the drying operation leaving a solid but pliable residue or" the magnetic material on the tape base.

in order to facilitate and to improve adherence of the magnetic material to the tape base, the surface of the tape base to be coated with the magnetic material may be pre-coated with a suitable adhesive material, such as a copolymer of polybutadiene with acrylonitrile, the methyl esters of acrylic acid, etc. The magnetic material is then laid on the adhesive surface and subjected to drying.

During either or both kcoating operations, the tape base is passed between a bottom support and the discharge opening of a feed hopper of the coating material, so that the coating is applied to the tape base as it moves thereunder. In the magnetic coating operation, the tape base is passed horizontally through a gap between the bottom support and the feed hopper.

Certain dilculties are encountered in the drying operation. As in the coating operation, the tape base is progressively moved over and around a series of rollers or guide supports. The tape base tends to vary transversely in tension and to curl in a manner that causes further diicultes in processing as well as in actual use.

2,741,217 Patented Apr. 10, 1956 While it is important to obtain a coating of magnetic material of optimum and uniform thickness on the moving tape base, it is also important that the coating be effectively dried without injury to the coating. Unless the coating is adequately dried before it comes in contact with a roller, guide support or other physical object, the coating is physically injured which in turn affects its sound recording and sound reproducing characteristics. v Difficulties and disadvantages of the kind enumerated, as well as others, may for the most part be avoided in the practice of the present invention; as will be made clear on referring to the accompanying drawings, taken in conjunction with the following description, in which:

Figs. 1A and 1B are longitudinal sectional elevations of a form of apparatus illustrative of a practice of the invention; f

Fig. 2 is an enlarged section on the line 2-2 of Fig. 1A, showing further details of the magnetic coating device;

Fig. 2A is a plan view of a piece of tape base showing uncoated, adhesive coated and magnetic coated portions;

Fig. 3 is a section on the line 3-3 of Fig. 1B, showing portions of the final drying and discharging zones;

Fig. 4 is a fragmentary elevational view on the line 4 4 of Fig. 3, showing an adjusting rod for a coated tape base guide support in the final drying zone;

Figs. 5 and 6 are fragmentary views of a magnetic testing portion of the apparatus, Fig. 5 being a sectional view on the line 5*5 or" Fig. 6 and Fig. 6 a plan view;

Figs. 7 and 8 are fragmentary views of a tape base aligning portion of the apparatus in the nal drying zone, Fig. 7 being a plan view and Fig. 8 a section on the line 8 8 of Fig. 7; and

Figs. 9, l0 and ll are detailed views of the magnetic testing portion of the apparatus shown generally in Figs. 5 and 6, Fig. 9 being a perspective view and Figs. 10 and l1 elevational views.

Referring first to Figs. 1A and 1B, the apparatus shown is divided into (l) a tape base charging zone A; (2) a pre-coating zone B; (3) a radiant-heat pre-coat drying zone C; (4) a magnetic coating zone D; (5) a heated-air preliminary drying zone E.; (6) a heated-air radiant-heat preliminary drying zone F; (7) a heated-air radiant-heat nal drying zone G; (8) magnetic testing zone H-l (Fig. 1B) and H-Z (Fig. 1A); and (9) a tape base discharging-winding zone I.

As will be explained in more detail below, the tape base is passed successively through (l) the tape base charging zone A, where it is carefully unwound from its roll; (2) the pre-coating zone B, where its upper surface is treated with a liquid adhesive material; 3) the radiantheat pre-coat drying zone C, Where some of the solvent is removed from the adhesive coating; (4) the magnetic coating zone D, where a coating of magnetic material, such as oxide of iron, is applied to the adhesive coating; (5)V the Aheatedair preliminary drying zone E, where some of the solvent in the magnetic coating is removed; (6) the heated-air radiant-heat preliminary drying zone F, where more solvent is removed from the magnetic coating; (7) the heated-air radiant-heat nal drying zone G, where the nal stage of the drying operation takes place; (8) the magnetic testing zone H-l and H-2, where the adequacy of the magnetic coating as to thickness'and quality are determined; and (9) the discharging zone I, where the dried coated tape base is wound into a roll.

The apparatus specifically disclosed in the drawings will be described in the order just outlined; that is, from the rst to the last zone:

Referring rst to Fig. 1A, a tape base 20 of any suitable material, such as cellulose acetate, paper, etc., in the form of a roll 22 is mounted on a shaft 24 supported between the two hollow members.

by a frame 26. The tape base extends over rollers 28,

i Y 30, 32 and 34, the latter roller being mounted on Va shaft tape base as Vit moves in wiping engagement with the bottom of the hopper, across its discharge opening. The tape base preferably is somewhat wider than the discharge opening so that its narrow marginal side portions remain uncoated. i

' The adhesive coated tape base extends through a precoat Vdrying chamber' S6, open at both ends vforY the passage therethrough of the tape base. The top of the chamber is fitted with a glass window 58, over which are Y Y mounted radiant heaters 6,`such as infra-red lamps, so

that radiant heat may pass into the chamber tofdr'yl the adhesive coating partially as the tape base`V proceeds through the chamber.

The partially dried adhesive coated tape base advances to a coating device formed in generall of a pair of spaced guide supports 62 and 64 approximately Vin alignment with theV discharge opening 66of a Vfeed hopper 68 supported at its rear by a bracket 70. A removable cover 72 on the hopper is slotted to receive a verticallydis- Y Vposed conduit 74 with a regulating'valve 76. The con-V duit is secured to a Vertical support 78 extending at its lower"H end to the frame. This conduit communicates with arsecond valved conduit 8,0 which in the instant Vconstruction extends through a ceiling 82 to the'oor above.V Y, v Y Y The second conduit connects with a filter 86. VWhile any suitable liltermay be used the current one is in the form of two juxtaposed hollow members containing several layers of fabric filters, such as lter paper, stretched to'catchlundesired solids'that might otherwiseind their way into the feed hopper and hence on the tape base.

The iilter is adaptedV ties in the coating. To this end'a bottom supportv 100 for the tape is provided below the feed'hopper, which maybe said to be free-floating because it can drop sui`n`- ciently to permit the obstruction to pass underneath without tearing the tape base and to signal an operator so Vthat; he may mark promptly'the affected spot for subsequent treatment to be described below; as more fully A disclosed in said copending applications. v It willrbe noted that tape base passes over the top of guide support 62 and then over adjustable bottom suppo'rt disposed directly below discharge opening 66V of feed hopper 68 and from there to and over guide support 64. n Y

Guide supports 62 and 64 are about the sameV height and are so arranged with respect to the bottom of feed .Y hopper 68 and bottom support 10i) that aV gap ofpre- Athird valved conduit S8 connects the filter with the Y bottom of a m'ixingior stirring vessel 92V having a shaft depending from its top;V the shaft being provided with a plurality of paddles arranged in different angles to each ,Y other in order more effectively to stir or mix magnetic. coating Vmaterial 96 contained therein.v lThe upper end of thershaft extends through the top'an'd is operatively Y connected with a motor 9S; A ciosable opening is provided in the top for introducing adispersion ofV mag'- netie material, such as magneticoxide of iron.

. Itseems that'no matter how carefullythe tape` baseV is made;- or processed preparatory'to coating'with the' magnetic material, as it approaches vfeed hopper V68 raised or lowered portions onV its Yupper or lower side, or both,

in the form of pimples, berries or blisters, for example, 'Y areA encountered` which not only alect the passage of the'.

tape base underneath the hopper, but also`the'sound#v recording and sound-reproducing characteristics of the tape. may jam against the hopper. andbe torn or otherwise Y damaged. The tearing of the tape base at this stage leads to'highly'undesirable complications. The magnetic dis' persion ows out kof the hopper and over-runs the adja' cent apparatus; the momentum of the on-coming tape base causes it to pile up; the pre-coating operation is',

It the obstruction is fairly large, the tape base determined minimum uniform height is provided and maintained between the top of tape base 20, or the top of bottom support 100, and the bottom of the hopper Y so that a coating of magnetic material of Voptimum thickness may be applied to the top of thetape base Vas it moves under the hopper. Y

A roller 102 is placed below the level of guide support 64 and is preferablyv made of such material as rubber so that it may grid the underside of the coated tape base. The roller is tightly mounted on a shaft 104 one end of Y which terminates in a ywheel, not shown. Roller 102 with its flywheel and roller 34 with its ywheel keep tape base 20 under tension Vand uniform speed, thusV helping to Y assure optimum coating operations.

` For furtherdetails ofthe magnetic coating device, brief reference may be made to Fig. 2 where it will be seen that adjustable bottom support extends across and well beyond the ends of discharge opening 66 in feed Y hopper 68, intermediate a pair insulated of'ope'n' box supf Vports and 112 secured at their bottoms to platformV 114 attached to the top of the frame.` The adjustable bottom support rests at its ends on; coil springs 116 and 11S held inrvertical position by base Vrods 120 and 122 integrally securedv to the top ofthe platform. Adjusting screwsr124 and 126 extend downwardly through threaded f Y holes in the tops of the open box supports into contact with the top of the adjustable bottom support. They are provided with lock nuts 128 and 130.

This construction permits adjustmenty ofV the bottoniV support with respect to the .bottom of feed hopper 68 byY turning the screws andlock nuts suitably so that a gap of predetermined minimum uniform height may be provided andVV maintained between theVVV top ofthe bottom supportz and the bottom of the hopper to place a magi netio coating of uniform Vthickness on the tape base. As

shown tape base 2@ is slightly wider than the feed hop- V p'erso that narrow marginal edge portions of the tape bae'extend beyondvthe sides of the discharge opening of Y the feed hopper and therefore remainY uncoated. TheV narrow marginal edge portions conform in general to the narrow marginal edge Vportions which receive no adhesive coating.

' the feedrhop'pe'r and the adjustable bottom support, it can-Y Y tion, whether to the side or in the center of the tape base, Y

of course, impaired; and the entireroperatiou must be stopped; lf the obstruction does not tear the tape base,

irregularities in the coating occur which greatly impair Vsound recording and hence sound reproduction. It is imperative that the finished tape base have a magnetic coating of optimum uniform thickness.

not be made smaller; unless ofcourse the screws and look nuts are disturbed.

But such a gap can be made larger by urging the bottom support downwardly against the coil springs. This happens-when an obstruction on the tape base arrives between the hopper and the bottom support. The obstrucwhether single or multiple, whether on the top side or the Y bottom side ofY the tape base, Ydepresses the bottom sup'- port and rides under the hopper-without tearing the tape VSpecial means'are provided, therefore, to'prev'ent tear- Y ing of the tape base and to overcome abnormal irregularibase; unless, of course, the obstruction is abnormallyV large, which seldom is the case. Y K

- As already indicated means are also provided to advise the operatonthat such an obstruction has `reached the .hoppen4 While such means may take various forms, Va

suitable device for the purpose ,isdisclosedin said co- Once sufch a gap is-established betweenV pending application.A Being made of metal, bottom support lili), and adjustable screws 124 and 126 may be utilized as conductors of elecrical current in a relay having terminals 132 and 134 secured to the open box supports, the terminals in turn being connected to leads 136 and 138 connecting with the remainder of the device, not shown.

In order brietiy to illustrate the operation of such signal means, it may be assumed that a portion of tape base Ztl approaching feed hopper 68 contains one or more obstructions, such as a pirnple, berry or blister of tape base material itself, or one c-r more foreign particles attached thereto. Since the coating of magnetic material on the tape base must be of substantially uniform optimum thickness, and that thickness amounts to only a few thousandths of an inch, it is apparent that the obstruction need not be very large in order to strike the bottom of the hopper, if the obstruction is on the top of the tape; or to strike the top of the bottom support, if the obstruction is on the bottom of the tape base.

lIt is imperative, therefore, that the mechanism employed be extremely sensitive so that the obstruction will pass between the hopper and bottom support without tearing the tape base and so that the presence of the obstruction is announced. Since bottom support 100 oats freely on sensitive coil springs 116 and 118, it is quickly and easily depressed or dropped to permit passage of the obstruction. Such dropping of the bottom support breaks the electrical Contact between the lower end of adjusting screw 124 and the top of the bottom support, or breaks the contact between the lower end of adjusting screw 126 and the top of the bottom support, or both. This breaking of contact is utilized to operate a signal which attracts the attention of the operator.

On hearing or otherwise noting the signal, the operator promptly inspects the coated portion of the tape base passing beyond the magnetic feed hopper to detect the precise location of the obstruction., He then attaches a marker on that part of the tape base, usually by means of a small adherent tab protruding beyond the edge of the tape base, so that the affected portion may be easily located later. The a cted portion is usually cut out, which may be done by removing a transverse section of the coated tape base. The resulting two ends of the main tape base, having a coating of the desired uniform thickness, are carefully spliced. This may be done, for ex- Hmple, by joining the two ends in an angular straight line, end to end, not overlapping relationship, with an adhesive piece of splicing tape overlapping the two ends on the uncoated side of the tape base.

Since adjustabie bottom support 190 is very sensitively balanced, the supply of magnetic coating material 96 in feed hopper 5S is advantageously maintained at an optimum level 146. This level, for example, may be directly at the bottom of supply conduit 74 and may be maintained with regulating valve 76. The weight or pressure of the magnetic material on the tape base moving under the bottom of the hopper, and hence the weight or pressure on the bottom support, remains substantially constant. The bottom support is balanced in such manner as just to be able to support the moving tape base and the supply of magnetic material in the feed hopper without being depressed. Such depressing or dipping of the bottom support as occurs is therefore attributable to obstructions on the tape base when they strike the feed hopper or the bottom support, or both.

So far as basic coating operations are concerned, it may be well at this point rieiiy to summarize what occurs by referring to Fig. 2A. Tape base 2h as it moves through the pre-coating zone receives an adhesive coating 142 intermediate narrow marginal edge portions 144 and 146, which remain uncoated. As the partially dried adhesive coated tape base moves through the magnetic coating zone it receives a magnetic coating 14S intermediate narrow marginal edge portions 150 and 152, which remain uncoated and which advantageously are of the same width as the other marginal edge portions. In other words, the magnetic coating is placed on the adhesive coating, the two coatings having substantially the same width. In a later operation, the uncoated marginal edge portions are cut olf and discarded, the coated intermediate portion only being retained.

Returning for the most part to Fig. lA and also Fig. 1B, it will be noted that the heated-air preliminary drying zone E extends from the left to the right, below the four zones aiready discussed, at an inclined angle downwardly toward the tioor. The drying apparatus is formed of a heater 169 provided with electrical means 162 for heating a supply of air entering inlet 164 at the top of the heater and passing through an outlet 166 at the bottom of the heater through an elbow extension 168 into a duct 75. A blower and a filter, not shown, are included so that air free of lint, dust and other foreign particles may be forced successively into and through the duct and other drying zones in the series.

The duct is formed of a bottom 172, a top comprising sections 174, 176 and 173 tightly iitting against each other to prevent escape of substantial amounts of heated air. The bottom portion of roller 1ti2 and the portion of freshly coated tape base adjacent thereto dip into a narrow opening in top section E74. The duet is also provided with a side wall to the rear and a side wail to the front, each being fitted with a window door E77 to provide ready access to the interior of the duct and to permit the opcrater or operators to see the coated tape base passing therethrough. The coated tape base is suspended between and out of contact with the walls of the duct. As the coated tape passes through the duct, heated air iiows concurrently therewith to citeer preliminary drying of the fresh coating.

Duct communicates with the heated-air radiantheat preliminary drying apparatus formed in general of a duct 18! supported in part by vertical walls 182 and 34, and enclosed except at the ends by a bottom 186, a rear side wall, and a front side wall, each being equipped with a window door i3d, and a top provided with a glass window it?. A plurality of electrically heated lights 192, such as infra-red lamps, are mounted on a conduit 194 directly above and centrally of the top window. This arrangement permits radiant-heat to pass directly through the window onto the partially air-dried coating on the tape base passing through the duct, thus drying the coating still further.

Duct 18d communicates with the heated-air radiantheat final drying apparatus formed in general of a relatively large rectangularly shaped chamber 200, deiined at the bottom by a door 201, a far end wall 294 having a window 296, a top 268 having a window 210, a near end wall 22 and iront and back side walls 214 and 216, both side walls being fitted with lower doors 218 and 220, middle window doors 222, 224, 226 and 22g and upper doors 239 and 232.

Far end wall 204 is provided with laterally extending and spaced supports 236 and 238 to which is secured a vertical conduit 249 located centrally ofl window 296. A plurality of electrically heated lamps 242, such as infrared lamps, spaced from each other at relatively short intervals are secured to the vertical support. The upper portion of the far end wall is provided with an exit opening 244 tted with a screen 246, and around which is secured an outlet pipe 24S preferably communicating with the outside atmosphere.

Top 268 is provided with vertically extending and spaced supports 256 and 252 to which is secured an electric conduit 254 extending centrally of top window 2li). A plurality of electrically heated lamps 256, such as infrared lamps, are secured to the latter support.

Near-end wall 2i2 is provided at its bottom with an opening 260 to permit passage of the coated tape base from duct 180 to drying chamber 26). The end wall is ditions.

also provided with a discharge opening 202 intermediate 'its top and bottom to permit Vpassage of the dried coated tape base from Vthe drying chamber' to the tapebase diS- Y 'reducer 274 mounted on a Vfoundation 276 near end wall Y l 212 of the drying chamber, a shaft 273, a sprocket wheel 239, an endless drive chain 232, a sprocket wheel 234, and a drive shaft 285 extending inside and lengthwise o the chamber near its bottom and back side walls, the

Vlatter shaft being supported in journals 28S and 290V attached to end walls 2l?. and Ziel. Y

The drive shaft contains a series of spaced belt guide grooves 232, each oi which is fitted with a drive belt; the

' VYtirstbelt in the series from left to right, as one views -Figs. 1B, beinga long belt 294 and the others being short belts 295. The long belts lits (Fig. 3) over and .in a belt lguide'groove 29S at the far end of a discharge roller 399,' preferably made of Va gripping material, such as rubber, mounted V'on Va shaft e552 held in .horizontal position by adjustable pivot members and 30d carried Aby supports Stl andV 33.6' attached to front and back side `walls 23.4 and Zie. The short belts tit over and ina belt guide gro-ove 3l?. at the far end of each of a corresponding series of rollers 3A horizontally suspended between adjustable pivot members 3M and 318 carried by 3 and 4). YThe upper end of the rod 4extends into and Ythrough'a clamp v350 and terminates ina handle V352,. 'Ihe clampY is provided with aV wing nut4354.' 'This construction permits (fEg. 3) vertical adjustment of the'rod and'henceY angular adjustment of guide support 346 in `a Vertical plane.

A marker 356, such'as apiece of tape, is placed on or near` the top -ofv the guide support with one edge'of the marker Y in alignment with the near edge of the tape basefo'r'V Where that VVedge of the tape base normally should be,A`

when'moving accurately in its path of travel. This helps the operator to adjust -the transverse position-of the guide support angularly so that the tape base is transverseV in Vuniform'contact with the guide support and will beY prop-V erly centered as it proceeds to succeeding rollersl From guide support 340 at the lower left hand cornerY of the chamberlFig. 1B) the coated tapefrbase ypasses to Yroller 35S at'the lowerright hand corner'of the cham- Vber. This causes the coated tape base to run substantially longitudinal supports 329 and 321 attached to the Yfront Y i and Vbacia side walls.Y All of therbrelts are to thefar side of and beyond the path of travel ofthe coated tape base.V

Vvllotation'of drive shaft Z'Sfby motor 27() is adapted,

therefore, to rotate directly rollers and fil. I' VThe speed of rotation of the directly driven rollers needs to be under accurate control so that an optimum speed may be adopted for a given set of operating con- For example, the nature of the coating itself, its formula, its thickness, the natureand efficiency-of the Y drying media, the mechanical arrangement of the guide device formed ingeneral of a vertical shaft 322 connecting at its lower end with gear reducerV 274 and at its i upperend witha vbevel Vgear 322. This bevel gear isin mesh with another bevel gear 324 connected to a trans- Y verse rod 326 supported Vby brackets 32S, 33d and 332 at- Y tached to a main horizontal support Bld-secured (Fig 1B) Y at one end to frame V26 and at the other end to end wall 22. inY present Vpractice this latter support also functions as a work bench forthe operators. 'The near end of the Y transverse'rod isrtted with arcr'ankwheel an'dhandle om.

The turning off the crank wheel permits adjustment of the gear reducer, so that the speed of drive shaft 2&6 and hence of power driven rollers Silit and 314 is adjustable.

So that the moving tape base may have a relatively long detention period in the chamber, at least one long enough for adequate ydrying of the coating/a series of other Yrollers and one or'more guide supports are provided at stra tegic places in the chamber. Thus, an adjustable guide support 349 is provided at the entrance of the final drying chamber, in the lower left hand corner as one views Fig.

` 1B.` Itis used to center and help maintain the tape base in tspredetermined'path of Vtravel as it advances from roller toV roller in the chamber. VWhile the one shown is a non-rotating rod, a rollerrcould of course beY employed.

The guideY supportis pivotally mounted (Fig. 3) at'its Yfar end 34E. Vto a U-'shaped bracket .sa-2Y secured to a plate 3 43 in turn -fastened to support 32E. A vertically 'dis posed rod 344 is pivotally secured to the near endd of the guide support. 'lt is bent to extend through a slot 343 in nearV end wall 212 toV the'exterior of the chamber (Figs.

parallel to and a short distance abovethe bottom of theV chamber for most of its etective length. A roller v3450 located a short distance above the latter roller cooperates coated tape basehorizontally along sideof top window A 210 to receive radiant heat from lamps 256'. A roller 366 located a shortdistance below andV slightly'to the rightof roller 364 deects the coated tape base horizontally Vto zroller 368,; and Vthence downwardly at an inclined langle 4for a short distanceV to a rollerV 371km, which is one of a-series ofi similar lrollers mountedtFig. V3) on horizontal supports 372 and 37d secured to iront and back side walls 214 and 2id VThese Vrollers are particularly `designed tocooperate with powerrdriven rollers 314.

yWhlea specific descriptionof the manner inV Which'the -rollersjust discussed aremonnted is not given; itwill be clear thatA algood deal of latitude is permissible vin .this regard. .lt is, ofcourse, primarily important that the rollersbe aligned at right angles to the moving'tape base in substantially uniform contact therewith andY that the rollers rotate easily. This helps to maintain equal tension on the tape base, thus inhibiting objectionable curlt Fig. 1B and reading-from left to rigl t that the last 4four inV vthe series of powerdriven rollers 314 near the bottom of the chamber do not have cooperating rollers in the series ofrollers 370 near the top ofthe chamber; and that due toa vguide supporter roller 375, relatively small in crosss section, located'between'the top fand bottom Vlevels of Y those four power driven rollers,fthe coated tape base is brought in contact with the tops as well as the bottoms or those driven-rollers; So far as the tests to be' described are concerned, Vthis. particular4 arrangement is not necessarypbut it is the apparatus'now in use and it is operative in practice. Y

The four'power driven rollers in question are designated Blf/ia, Slb, Siria and 32413.' New referring to Figs. 5 and 6, which detail some of the structural features to better advantage, it will be noted that a cross-support -380 extends between and above rollers Sfida and 3145,which is'attached-at its ends to thefto'ps of vertical posts 382 and 384 secured atV their bottoms to longitudinal supports 321') and 321; and that Va similar cross-support extends 9 between and above rollers 314b and 314e, which is attached at its ends to the tops of vertical posts 388 and 390 secured at their bottoms to longitudinal vsupports 320 and 321. p Returning to cross-support 386, a pair of spaced brackets 392 and 394. depend therefrom. They are spaced on the cross-support so as to overhang the edge portions of thecoated tape base. Magnetic charging heads 396 and 398 are mounted at the bottoms of the depending brackets in such a position as to contact and slightly to depress the tape base between rollers 34a and S14-b. The magnetic charging heads are quite similar to the magnetic recording heads used on current magnetic tape recording machines, and are'adapted to energize magnetically the running portion of the coated tape base within their field, as will be described in more detail below.

In a similar manner, a pair of spaced brackets 408 and 402 depend from cross-support 386. Magnetic pickup heads 404 and 406 are mounted at the bottoms of the depending brackets in such a position as to Contact and slightly depress the tape base between rollers 314b andV Y.

314C. The magnetic pick-up heads are quite similar to the charging heads and to the magnetic pick-up or sound reproducing heads used on current combination magnetic recording and sound reproducing machines. They are adapted to pick up magnetic energy from the running portions of coated tape base just energized by the charging heads, which energy may be measured and appraised as will be described below.

On tracing the course of the coated tape base in Figs. 1A and lB from magnetic coating hopper 68 in zone D to rollers 314:1, 31417, 34c and 314d in zones G and H-l, it will be noted that as the tape base leaves the hopper its top surface contains the coating; that this becomes the undersurface asthe tape base advances through drying zones E and F; and that in zone G the coating is kept out of contact with guide support 348 and rollers S, 360, 362, 364 and 366; that the coating then contacts an object for the iirst time, namely, rollers 368 and 374) but not 376; and that the coating then contacts the tops and bottoms of rollers 314e, 314i, 3I4c and 314e'. ri`his arrangement permits a relatively long path of travel and hence a substantial amount of drying of the coating before it contacts rollers 368 and 376er.

Since rollers at that stage of the final drying operation have no harmful eiect on the coating when in rolling contact therewith and since magnetic heads 396, 398, 464 and 486 (Figs. 5 and 6) would have a harmful effect on the coating when in rubbing contact therewith, the rollers and the magnetic heads are so arranged as to cause the coated surface of the tape base to be in rolling contact with rollers 3I4a, 3I4b, 314C and 31411? and the reverse uncoated surface of the tape base to bev in rubbing contact withthe magnetic heads.

A Figs 9, l0v` and l1 may now be referred to in further explanation of the foregoing. Tape base 29 is shown as moving from left to right (as also in Figs. 1B, and 5 ando) with its magnetic coating 148y at the bottom and magnetic heads 396, 398, 484 and 406 at the top of the tape base in Contact therewith. In other words, the magnetic headsare in contact with the uncoated surface of the coated tape base. As more particularly shown in Fig.v9, charging head 396 is provided with a gap 410 adjacent the coating and a wire coil 412, the ends of which terminate in main leads 414 and 416 connecting with a source of electricity 418. Branch leads 420 and 422 connect the main leads with a meter 424. In a similar manner charging head 393l is provided with a gap 439 adjacent the coating and a wire coil 432, the ends of which terminate in main leads 434 and 436 connecting with a source of electricity 438, advantageously the same as the other source. Branch leads 440 and 442 connect the main leads with'a meter 446. Since Ymagnetic charging heads 396 and 398 are in contact with the uncoated side of the coated tape base,

the magnetic field produced around the gaps 410 and1430 must be somewhat larger than would be the case in conventional methods of sound `recording when'the magnetic recording headsare brought in contact withthe magnetic coating. In other words, the magnetic eld produced by the present charging heads must be suiiiciently large to penetrate not only the body of the tape base itself but also its undercoating of magnetic material. This is illus-` trated in Figs. l() and li. For purposes of illustration, magnetic head 396a in Fig. i0 may be considered as hav ing a narrow gap 410a, substantially the same as that used in a conventional magnetic recording head. Magnetic :lield 456a does not adequately penetrate the tape base, if at all. it does not, therefore, adequately energize magnetic undercoating 148, if at ail. n

In the case of Fig. 11, on the contrary, gap 410 is sub stantially wider than gap 4Min-thus assuring the generation of a magnetic field 450 suiiciently large and strong completely to penetrate both the body of tape base 20 and its undercoating 148 of magnetic material. rIhis is necessary, asit is in the case of charging head 398 and its gap 43), in order adequately to charge the running side portions of the coated tape base magnetically for the pickup tests. Y y i The meters are placed where they may be seen readily by the operator. In Pig. 1A they, but not the leads thereto, are shown above the magnetic feed hopper. They are preferably' mounted on a panel.

In operation current of desired wavelength is derived from sources 418 and 438 to energize charging heads 396 and '398 so that the coating on the portions of the tape base adjacent thereto may be charged with adequate signal strength. The charging heads are identical so far as possible so that each may discharge signals of the same strength. n other words, so far as possible the two charging heads are operated under the same conditions. if necessary they maybe suitably calibrated to obtain this result. Meters 424 and 446 are useful in determining whether there vis a change in quality of the magnetic material when the coating itself remains at its predetermined thickness. A change in signal strength from a standard value for .that thickness indicates'a change in quality of the magnetic coating material. So far as the magnetic energization of the coating is concerned, therefore, the main remaining variables willbe in the thickness of the coating as between the two marginal edge portions of the coated tape base. Any differencel in magnetic energization of the coating at the marginsshould, therefore, be reflected in the pick-up tests that follow.

Returning to Fig. 9, pick-up head 404 is provided with a gap 456 adjacent the coating and a wire coil 458, the ends of which'terminate in main leads 460 and 462 connecting with an amplifier 464. Leads 466 and 468 in turn connect the amplifier with a meter 470. In a similar manner pick-up head 406 is provided with a gap 476 adjacent the coating and a wire coil 478, the ends of which terminatein main leads 480 and 482 connecting with an amplifier 484. Leads 486 and 488 in turn connect the amplifier with a meter 49).

As in the case of the gaps of the charging heads, the gaps of the pick-up heads must be sufiiciently wide to t compensate for therthickness of the body of the tape base as well as the coating. They must be able to encompass enough of the magnetically energized field in the coating on the underside of the tape base to pick up sound signals (field strength) truly representative of 'the strength of the magnetically energized marginal side portions of the coating. As it is the signals picked up are amplified for convenient indication by the pointers 'of meters 470 and 490.

For comparison purposes the pick-up heads, like the charging heads, are identical so far as possible so that the main variables encountered are the thickness of the coating itself, and the quality of the coating, such as its magnetic material content, the dispersion of the magnetic i in Vzone nung. 1A).

1 1 material in the coating, etc. The pick-up heads may be calibrated to assureidentical operating efticiency. Thepointersof meters 424 and A46 for charging heads 396 and 398 `point to the same values, thus indicating that both side portions of coating 148 are being charged with-identical amounts of ymagnetick energization. The

pointers of meters 470 and 490 for pick-up `heads 404 Vandrfiralso point tothe same values, thus indicating 'Y that both marginal side portions of the coating are deliveringV identical amounts of magnetic energization. The

Vbatch of Vmagnetic'. material -"dilering substantially in qual;

ity from that rpreviously introduced. The meter readings Y promptly-indicate such archange in quality vand the operaf latter fact further indicates that both marginal side por- Vtions of Vthe coating are identical in thickness and quality,VV

and that all is well with the magnetic coating operation Y IfV the coating there applied to the tape base has lan optimum'uniform thickness -and -is uniform in quality, present practice shows that that opti mum V,uniform thickness'and/quality -are maintained onY the -tapebase-as it passes under the charging and pick-up heads. Operating conditions are ideal, therefore, andY such as the operators seek to establish'and maintain.

While such ideal operations normally can be fairly well maintained after they are initiated,some adjustment is usually necessary when startingroperations and some- Y times during the midst of operations. In any event,

the magnetic tests under consideration are highly usefulV in determining whether allV is well so far'as uniform thickness Yof coating and quality are concerned; and, `if

Vnot,.in indicating what adjustments are necessary in the coating operation to obtain or reobtain a coatingY of'uni V"form thickness and quality. t

Y, l Thus, if 4the reading on meter-470 -varies Vfrom Ythat Yon meterV 490, the operator is Vat' once advised that lthe Y t thickness of the coating under pickfup 404 is Vnotthe vsame as that'under pick-up head 406. `-He, therefore,V

goes to zone D to make whatever adjustmentsV are necessary Vin thecoating step to obtain a coating of uniform thickness'. lf, for example, the meter readings indicate that -the coating is thinner under'pick-up head l4 04 lthan l under pick-up head 406, theoperator (Figs. v1A and 2) Vturns adjusting screw 1 24 on'the same marginal side of the tapegbase promptly to depress that end of bottom guide support V100. To this end lock nut 128 is turned upwardly and the adjusting screw is then turned downwardly. rIr'he amount of Vturning in both instances is very small -because the 'ultimate coating desired vis itself quite thin. In any event the adjustment-increases the Jdeipth of the gap between that side of ,feed lhopper 68, and the Ybottom guide support, thus increasing the `thickness ofthe coating atthat marginal side of -th'e tape-base.

Y -'l`;he operatorY (Fig. lA)"then observes what etfecthis l adjustmentV has on the pick-up meter readings. ,The

meters are placed advantageously near the feedhopper so that'he can make the readings readily. -He must, of

. course, allow enough time for'the adjusted coated portion of the-tape base to reach the 'magnetic-heads;

Vdoes -not take long, dependingof course on the speed of travel Vof Ythe-tape base; and he soonl observesa ehange inthe reading Afor meter 470. YThe new reading will VYindicate whether the adjustment was sufficient, insutiicientor excessive. If not 'the' formen'hemakes another adjustment. By'trial and error the operatorsoon obtains a proper adjustment.V `Iftthe,discrepancy in thickness orquality of coating is substantial, the. affected part of the coated tape baseis discarded. Y i Y A From the foregoing, it willhe clear that the operator relies on the meter readings to guide him in makingn whatever adjustments are necessary in the c'oating'operation Vto assure a coating of uniformv thickness. -ToV regulateV adjustment yscrews YZ/-ltand 126 of the magnetic'rfeed hopper, he is guided almost entirely 4bythe meter readings; and they can'be made easily and quickly. i i

As already indicated, the coatingmaybeof uniform thickness but notin quality. -Flfhisoccurs, ,foi-example, when the magneticA material coming from theffeelI hopper changes in quality, due perhapsvto the'introductionofra tor can be' guidedaccordinglyt Y Taking up next the matter of keeping the coa hase in accurate alignment on'the rollers, it will be noted ion referring tofzone G of Fig.lB, and reading from, Yright to left, that after the coatedtap'e baseleavesrthel magnetic charging and pick-up vheads just discussed,"-it passes up andV down and progressivelyV advances from a power drivenroller 314 in theV serieslbelowttofa roller 37% Vin the series above until it reaches a rounded LalignA ing guide 56% disposedfbetweenthe rst and Ysecondlrollers 370, on reading from left to right, in the upper series;

The aligning V'guide diters in construction from YYrollers 370V Yand Yis speciallyrdesignedto help'keep thecoated tape base' Y 'l in alignment on rollers that precede and Yfollowjit. Q

Aligning guide 5th) and jits accompanying structure are detailed in Figs. 3, 7 and 8.' Unlike rollers 3770 vin the upper series, the aligning guide is Vnot suspendedlat its ends'between pivot membersrfor example, likeroller e in Fig, 7. The aligning guide, however, is pivoted near one end by a vertical pin 502 to abracket 504'attached to'horizontal support 372 so that the guidexmay move about the pin angularly in a horizontal plane. The

i other endV of the guide is slidablyV mounted in a channel I S06 secured to horizontalsupport 374. A rod 5081er;-

A the Yguide is pivoted to the right, asone views Fig, 3, it

its ends, but nearer the far end with the bellows.

tends horizontally through and is attached to that endof the guide. One end of a spring 510 is attached to one end of the rod and the other end of the spring is attached j to an anchor 512 secured to horizontal support 374. MThe other `end or" the rod is attached to a bellows 514 carried by an underslung bracket 516 (Fig. 8) secured to the underside' of the channel.

Now, turning to Fig. 3, it will be noted that Ya motor 520 is operatively Yconnected to Y ai suction or exhaustffan 522 from which extends a main suction Yconduit*5;24which terminates Vin two branch conduits 5,26 and 5 28 The' first branch conduit (Figs. 7 and 8) extends upwardly to and connects with bellows V514. The second branch conduit (Fig.V 7) extends upwardly to and connects with a passageway or hollow tube'530 extending Vcompletely Y throughand attached to aligning guide 500 intermediate The open end ot'` the passageway or hollowV tube terminates in a small hole'532 inthe right sideof the'alig'ning guide against which :the tape base slides as it rises to and passes over the guide, in the direction of arrow 534. The

Y hole iis locatediwhere the `far outside vedge 5361of-th` e adjacentportionV of coated tapejbase 20 shouldibeipasising when properly centered on the'guide i" A The function of the structure just'descr'ibed is :to keep the edge'of the farmarginal Vside ofthe tape Y,base cntinually over the hole and henceto keep'thc moving .tape hase centrally aligned on therguide as well Yas on rollers that precede and'follow'the guide. This'islposisiblebecause of the automatic manner in which the guide may be pivoted. Before` going into the automatic 'phasefof the operation,` however, it may be'helpful first' toconsid'er what happens when the guide is operated'manuallyl v If exerts/greater pressure on the far marginal side thanon the near marginal side of the tape base, thus causing the tape base to move laterally toward the nearside; namely, away from hole 532. reverse conditions obtain.

ted Vtape lf the guide is pivotedA to Vthe left, Y p Pressure of the guide on theV Vtape base is lessened at the far marginal side, and the when conditions call for suction. Whether branches 526 and 52S are under suction at a given moment depends on the condition of hole 532. Y

If,-for example, the hole is only partially covered, say half-covered, the branch conduits will not be under effective suction because air is drawn into the hole and down its branch conduit 528. This air, therefore, prevents the development of eifective suction in that branch as well as in branch S25, thus leaving the guide pivoted slightly to the left of what may be called dead center; its normal position under the tension of the spring.

If, next, the far marginal side of the tape base moves over to cover the hole, branch conduits 526 and 528 are placed under suction. This suction reduces the air pressure in bellows Sid, thus causing them to contract. When this occurs, the guide pivots to the right and the tape base creeps toward the near end of the guide support; namely, away from the hole. Since the hole is then only partially covered, air enters branch S28 and thev suction in both branches 526 and 528 is broken. The spring then pulls the guide back to its former -position, slightly left of dead center. As this'occurs, the tape base creeps toward the far end of the guide, thus again gradually covering the hole. Branches .526 and 528 are then placed under suction, causing the guide to pivot back to its former position slightly right of dead center.

In other words, aligning guide 500 swings back and forth like a pendulum, its arc of swing, however, being very small; and the tape base oscillates from side to side, its range of movement likewise being very small. Since the hole is quite small and it need be only partially uncovered to break the vacuum in the branch conduits, the pendulum movement of the guide and the side to side movement of the tape base are hardly perceptible by the eye. They have the eiect, however, of keeping the tape base in its prescribed path of travel; which effect, moreover, tends to be transmitted to the tape base passing over preceding and following rollers. Y

Going back to zone G of Fig. 1B, it will be noted that the coated tape base leaves adjusting guide 500 for the iirst roller 370 in the upper series, reading from left to right; then passes down and under the first two power driven rollers 314 in the lower series, again reading from left to right; and next moves up and over power driven discharge roller 300 at discharge opening 202 in near end wall 212. It will be recalled (Fig 3) that the discharge roller is mounted on shaft 302 carried by side supports 308 and 310 attached to front and back side walls 214 and 216 of the final drying chamber.

A holddown roller 549 (Figs. 1B and 3) of adequate weight extends transversely across the top of the discharge roller. It rests by gravity, and therefore exerts a holding force, on the coated tape base passing over the discharge roller. The ends 542 and 544 (Fig. 3) of the hold-down roller are smaller in diameter than the main portion and t in drop-slots 546 (Fig. 1B) in side supports 308 and 310 (Fig. 3), the slots acting merely as retainers for the holddown roller ends and being suciently deep so that the holddown roller is supported freely on the discharge roller and the two rollers together are adapted to grip the coated tape base. This becomes important, for example, when it is desired to separate the portion of coated tape base already discharged from the drying chamber from the oncoming portion. The tape base outside of discharge opening 202 may be cut without fear that the end next to the opening will be drawn back into, and cause a piling upof oncoming coated tape base in, the final drying chamber. The arrangement described permits cutting of the tape base discharged from the drying chamber and at the same time keeping the oncoming tape base within the drying chamber under its normal tension.

Again returning to Fig. 1B, coated tape base 20 passes from discharge roller 300 and holddown roller 540 through opening 202 in the end Wall of the final drying chamber to discharge zone `1 to be wound into a roll. The apparatus for-this purpose includes a platform S50 and a brace 552 attached below the opening to the endv wall of the chamber; a motor 554 operatively connected to a gear reducer 556 with a shaft and a sprocket wheel; an endless drive chain 558 (Fig. 3) mounted on the Sprocket anda second sprocket wheel 560 mounted on a shaft 562 supported in journals 564 and 566; the right end of the shaft, as one views Fig. 3, being free and integrally tted with a core 568 adapted to fit in and be keyed in a hub 570 around which the coated tape base is wound into a roll 572. The core is' provided with an integral stop 574 and an integral key 576, spaced oppositely from one another. The hub is in turn provided with afkeyway 578 adapted to receive the core key.

The apparatus also includes a footage counter 580 secured to the lower end of a bracket 582 pivotally mounted at its upperend 584 to the upper end of an upright post 586 secured atzits'bottom tothe platform. A journal 588 is secured to the bracket, through which extends a shaft 590 operatively connected at its left end to the counter and at its right end to a friction disc 592, covered for example with rubber, resting on and adapted to be turned by the roll of coated tape'. Due to the manner in which the bracket is pivoted, the disc, and hence the shaft and counter, rises as the Vroll of coated tape base increases in size.

If desired, uncoa'ted roll 20 of tape base may be converted entirely into a coated roll 572; that is the overall length of the coated roll will be substantially Vthe same as that of the uncoated roll. In practice it is usually desirable to start operations with a relatively large uncoated roll and to obtain therefrom a number of smaller coated rolls of specified footage. Footage counter 580 is useful for the purpose. When the coated roll reaches the desired amount of footage, the coated tape base is cut transversely as it leaves discharge opening 202 in the final drying chamber. i

A few preliminary steps are advantageously taken: Motor 554 is stopped, hub 570 is loosened from core 568 and its key 576; roll 5,72 and its hub are pulled toward the near end, away from the core; another hub is keyed to the core; the coated'tape base is cut as it continues to leave the discharge opening; the free end of the tape is secured to the hub; the motor isvstarted and speeded to take` up the slack portion of coated tape base outside of the discharge opening; and the speed of the motor is' then adjusted to wind the coated tape base at its normal rate on the new roll.

If, as indicated above, an obstruction on the tape base impairs the thickness of the coating of magnetic material deposited thereon as the tape base passes under magnetic feed hopper 68 and over adjustable bottom support 100, the operator, in response to a signal initiated thereby, locates the obstruction and places a marker, such as a tab, over the peripheral portion of the coated tape base for easy detection. Also, if the magnetizing tests described above show sections of the tape base to-be improperly coated, they are similarly marked by the operator. The coated roll of tape base after drying is unwound to lay bare the section or sections afected. They are cut out and the ends of the main portion of the tape base are suitably spliced, preferably in end to end, butt-end, relationship so that the thickness of the coating at the splice joint is of the same uniform thickness as the remainder of the tape base.

In a present practice of the invention, the tape base is six inches wide. Each roll of coated tape base, after drying and after the affected sections are removed and the free ends are spliced, is cut as it is unwound into a plurality of pieces of tape of desired width and each piece of tape so cutis wound simultaneously into a separate roll of desired footage.

We claim: Y Y l -1. In apparatus Vforproducing vmagnetic sound-recording and sound-reproducing Vt'ape'by passing a relatively long andV narrow tapev base successively vthrough a'coat- 'ingmachine and a drying machine, one side of the -tape base being coated with a layer of a dispersion of freeiowing magnetic'material while moving through the coating machine and the coating being dried while moving through the drying machine,-'the improvement'comprising a drying'machine provided with a dryingy chamberVV hav- Ving an entrance for the freshlyI coated tape base and an exit for thedried coated tape'base; a gripping roller for `the freshly coated` tape'base atitsentrance to help keep the ytape base under YtensionasY vit enters e and moves through the chambenan entrance lin .the chamber for'the Y introduction of heated drying air; a vent'in the chamber Afor Y the withdrawal of spentV drying air Vand vapors` chamber includes an elongated entrance duct extendin Y from Lthe coating machine; lthe duct communicates Vwith volatilized ,fromY Vthe coating; aj plurality Yof Vspaced supf YYports; Vat parallel horizontal `'levelsV in a generally vertical plane in the drying chamber over which the coated tape base may be adva'ncedfwhile'under,tension in aV prede- Y'terxnined and extended sinuous path of travel in a Vcorr'e- 1 sponding vertical planewith its at sides in .a substantially continuous transverse .horizontal `plane and hence .with no twist from the entrance to the exit, someof the spaced supports being inthe form of power-driven rollers to p ropel'the coated tapelbase .along .the path of 1travel;1the

supports along a substantial distance of the initial path s of travel in the` chamber` being .positioned along -the uncoated side of the tape'base'zsothat `the vfreshly applied dispersion of magnetic material on .the other side vmaybe Y given' ample time to dry'befo'recoming in contact with a physical ohjectyan A'adjustable guide `support 4pivotally mounted across the path .of travel toregulate the rtension transversely of the coated tape baseto keep it ,in the path of travel; and a pair of juxtaposed `gripping Arollers at the dried'tapeg'baseexit in the Vpath of travel to grip the tape baseV and vto prevent tape base beyond the gripping rollers from backing up in the` drying chamber, at least one of `the gripping rollers being power driven yso that dried tape base may be continuously advanced through its exit'. Y -Y Y 2. Apparatusaccording to claim 1, in which the heated drying air entrance is adjacent the coated tape .base entrance, and an air heater-communicates with theY drying 'air entrance so vthat'heate'd air Vmay move in a Vgenerally Y.concurrent direction with theinoving tape'base.

3. Apparatus according toclaim'lrin which .the drying an air heater sothat the coated Ytape hase may be subjected to heated air drying as it passes therethrough from the coating machine to the main portion of the drying chamber; and-the venty for spent drying air and volatilized vapors isrlocated inthe main Vportion ofrthe drying.

chamber. e

4. Apparatus'accoirding to claim 1, in Vwhich the powere' driven rollers are`operative1y connected with a powerdriven shaft extending transversely of Vthe drying chamber.V

5.` vApparatus according to claim 1, in which radiant heating emeansare associated with the chamber so that ythe fresh coating on the tape base 'may he subjected to 4heated air as -well as radiant heat dryingwhile in transit ythrough the drying chamber. Y 6.`V Apparatus according to claim ,1, in which thepower-V driven rollers have centrally recessed ends and the rollers are suspended Vby pivot members extending into the re- -cessedrrends f Y `-7.` ApparatusV according to claim ,6, in which the pivot members rest Yin fixed end supports and are provided.

with -rneans for adjustingptheir position with respect to the rollers and the end supports.

Sali-,Apparatus according toclairn l, in which the adjustable guide support is pivoted at one: end and freely rnovable at `the.VL other end so thatA the guide support is angularly adjustable in aV plane substantially at right angles-to the path of travel of the coated tape base as 'it reaches and contacts fthe guide support.

9. Apparatus according to claim 8, rin whicha plu-- rality of ksuch adjustable guide supports spaced fromone another are provided inthe drying chamber.Y

'Nicholas v r Mar so, 195118 

1. IN APPARATUS FOR PRODUCING MAGNETIC SOUND-RECORDING AND SOUND-REPRODUCING TAPE BY PASSING A RELATIVELY LONG AND NARROW TAPE BASE SUCCESSIVELY THROUGH A COATING MACHINE AND A DRYING MACHINE, ONE SIDE OF THE TAPE BASE BEING COATED WITH A LAYER OF A DISPERSION OF FREEFLOWING MAGNETIC MATERIAL WHILE MOVING THROUGH THE COATING MACHINE AND THE COATING BEING DRIED WHILE MOVING THROUGH THE DRYING MACHINE, THE IMPROVEMENT COMPRISING A DRYING MACHINE PROVIDED WITH A DRYING CHAMBER HAVING AN ENTRANCE FOR THE FRESHLY COATED TAPE BASE AND AN EXIT FOR THE DRIED COATED TAPE BASE; A GRIPPING ROLLER FOR THE FRESHLY COATED TAPE BASE AT ITS ENTRANCE TO HELP KEEP THE TAPE BASE UNDER TENSION AS IT ENTERS AND MOVES THROUGH THE CHAMBER, AN ENTRANCE IN THE CHAMBER FOR THE INTRODUCTION OF HEATED DRYING AIR; A VENT IN THE CHAMBER FOR THE WITHDRAWAL OF SPENT DRYING AIR AND VAPORS 